Method of extinguishing of fire in open or closed spaces and means for performing the method

ABSTRACT

The invention relates to a method of extinguishing fires in closed or open spaces using water and foam. The method is characterized in that water mist is first produced with the air available in the space without air supply from outside until the temperature in the combustion gases has fallen below a predetermined level or during a predetermined period of time, whereupon foam is produced with the air available in the space without air supply from outside and with a suitable speed for filling the space and extinguishing the fire. The invention also includes a means for performing the method comprising units for producing water mist and foam in the space and a closing or controlling valve (33) which, in dependence upon the temperature in the combustion gases or period of time elapsed from the start of the water mist production, controls the amount of foam liquid added to the water.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and a means for extinguishingfires in open or closed spaces using water and foam. The method isespecially suitable for extinguishing fires in factories, ships, roadtunnels etc, where mist and foam units and further means may bepermanently mounted.

2. Description of the Prior Art

It is known to use water also in the form of water mist and foam whenextinguishing fires in different spaces. Also, different forms ofnon-combustible gases such as carbon dioxide and halones are used forthis purpose.

In spaces which are regarded as being fire hazardous and which have beenprepared for extinguishing of possible fires, water can be introducedfor example by means of sprinklers. When the sprinkler water has a lowpressure it will flow out in the form of a shower, whereas when it has ahigh pressure water mist will be produced. This water mist is producedboth as a result of the high pressure and as a result of the water beingejected against a net or the like. The water then suitably has apressure of 6 bar.

The water mist can also be made in units with a lower water pressure offor example 1.5 bar, whereby large amounts of air have to be blown intothe unit from outside. Foam is produced in the same way, although purewater is then not used, but instead water to which a foaming agent hasbeen added.

Foam for extinguishing purposes can also be made by means of specialportable containers but the foam is then produced in another way thanabove.

Although the aforementioned extinguishing systems can extinguish mostfires, they are, however, not perfect. It has i.a. shown itself to bethe case that the hot combustion gases are the main cause of large scaledamage from fires. It is therefore necessary to cool the combustiongases down quickly with normal sprinkler systems producing waterdroplets as well as water mist, the combustion gases are cooledeffectively and, if the sprinkler system is combined with foamextinguishing, so-called pool fires can be extinguished. The expressionpool fires includes fires which occur for instance on a floor in theshape of, for example, a burning liquid pool. This extinguishing systemcan however not cope with hidden fires, for example fires which occur inarticles in a pile of pallets.

Only foam can extinguish all fires but the foam cannot cool thecombustion gases so that the damage due to these hot combustion gaseswill occur anyway.

It has therefore been a long-felt want to be able to extinguish alltypes of fires and achieve a quick cooling of the combustion gasesresulting in minimal damage.

Besides the above-mentioned problems the difficulty of arranging anautomatic and hence quick action of the extinguishing system also arisessince a risk exists that this can kill or seriously injure persons whichare present in the burning space. Only foam can have this effect,whereas on the other hand water mist does not have this effect.

Some gases, of the Halon type and possible substitute agents, do notkill or seriously injure people, but since releasing a gaseous systemlargely means that all available extinguishing gas in the space isreleased, a new release cannot occur until after refilling. Other gasesof the carbon dioxide type or other inert gases cannot be used in spaceswhere people are present due to the inherent reduction of oxygen.

SUMMARY OF THE INVENTION

According to the present invention the problem associated with theaforementioned systems has been solved and a method for extinguishingfires in closed or open spaces using water and foam has been achieved,which method is characterized in that the water mist is initiallyproduced without air supply from outside with the available air in thespace until the temperature in the combustion gases has been loweredbelow a predetermined level or during a predetermined period of time,whereupon foam is produced in the space without air supply from outsideand at a suitable speed for filling the space and extinguishing thefire.

According to the invention the foam production should start after acertain period of time of water mist production, for example about 30seconds.

According to the invention, the foam production may start in dependenceupon the temperature in the combustion gases when this has been loweredto a suitable level of, for example, 300°-400° C.

According to the invention the foam should be produced in such an amountthat the level of foam in the space rises at a speed of at leastapproximately 1.5 meters/minute.

The invention also includes a means for performing the method comprisingpossibly one or more fire indicators in the space which is to befire-protected, one or more units for producing water mist and/or foamusing the air available in the space without air supply from outside,and pipes for supply of water or foam liquid to the units, which meansis characterized by a closing or controlling valve which is controlledin dependence upon the temperature in the combustion gases or by thetime which has elapsed from the start of the water mist production in apipe from the foam liquid tank to the supply pipe(s) for water to theunits.

Using this proposed system, water mist is accordingly first used tolower the temperature of the combustion gases and quickly control thefire. After having checked that all persons are safe, the addition offoam liquid is triggered so that the foam level in the space quicklystarts rising and a complete fire extinguishing is effected.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described in more detail with reference to thedrawings, in which

FIG. 1 shows a side view of a foam and mist unit respectively seen fromthe side, and

FIG. 2 shows the same unit seen from above or below and

FIG. 3 shows schematically the supply means for water and foam liquidrespectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a unit consisting of a supply pipe 1 which is shown insection and which has a branch pipe 2 for supply of water to theejection nozzles which are shown in more detail in FIG. 2. FIG. 1further shows a support 3 on which a container 4 being open at both longsides has been attached. On one long side, however, a net 5 in the shapeof an elongated cone has been attached. When water having a highpressure coming from the pipes 1 and 2 is ejected out to the left inFIG. 1 into the box 4 and further against the net 5, small droplets areformed on the net producing a water mist.

FIG. 2 shows the same arrangement as in FIG. 1 seen from above or frombelow and the same references denote the same elements as in FIG. 1.Furthermore, FIG. 2 more clearly also shows a pipe 6 which is connectedto the pipe 2 and three nozzles 7 for the water ejection.

If instead of pure water a mixture of water and a foam agent is ejectedthrough the nozzle 7 a foam is formed on the net 5. The foam agent can,according to the invention, be a conventional one, for example an agentwhich is marketed under the tradename Hot-Foam. This agent is suitablyadded in a concentration of 2% to the water.

FIG. 3 shows schematically an example of the supply of water and foamingagent according to the invention. In the drawing a container for foamingagent 31 is shown. From this a pipe 32 leads to a valve 33 whereafterthe pipe 32 ends in an ejector 34. Water is flowing through this ejectorin the direction of the arrows through the pipes 35, said pipes beingconnected to the main supply pipe 36 to the unit or units. In this pipe36 a pump 37 and a valve 38 are also shown.

When a fire starts in a space in which the unit according to FIGS. 1 and2 is mounted this will be indicated in some way suitably by means of afire sensor in the space and a water stream is started in the pipe 36,and this water is arranged to make the water mist by the unit accordingto FIGS. 1 and 2. When the combustion gases have been cooled down to apredetermined temperature of, for example, 300°-400° C., or a certaintime has elapsed after the start of the water mist, for example 30seconds, the valve 33 in the pipe 32 is opened and foam liquid from thecontainer 31 will then flow into the ejector 34 due to the vacuum whichexists there and mix together with the water stream. This will then flowfurther in the pipe 36 together with the fresh water. The valves 38 and33 are adapted to give a suitable amount of foaming liquid to the water,for example 2%.

More units can suitably be arranged in the space depending upon its sizeand its shape. So much foam should however be made that the level offoam which starts from the floor should rise with a speed of at least1,5 meters/minute. The amount of foam which is usually produced by aunit is about 60 m³ /minute and the number of units must then be adaptedto this. Also other types of units can be used, for example thoseaccording to FIGS. 1 and 2 stacked on each other and united in two orthree levels.

The means for the supply of water and water/foaming agent respectivelycan be constructed in a number of ways. The common aspect for the meansmust, however, be that a valve similar to the one which is denoted 33 inthe FIG. 3 must be present in the pipe from the foaming liquidcontainer.

The method according to the present invention combines the greatestadvantages with earlier known systems such as water mist, sprinklers,gas and foam and also entraps the harmful combustion gases in the foamand cleans them. Due to the fact that no air is blown into the system orthe space, no combustion gases will be released since those, asmentioned above, are entrapped in the foam.

The system can also extinguish hidden fires, it requires less watercapacity per surface unit compared to, for example, sprinklers, itbrings about a cooling effect and it can easily be started and stoppedand also tested.

The system includes no moving parts and requires no air for the unitsand it is easy to maintain and install.

The invention is not limited to the embodiment shown but can be variedin different ways within the scope of the claims.

I claim:
 1. A method for extinguishing a fire in a closed or open spaceusing water and foam, comprising the steps of:(a) initially producingwater mist using air available in the space until a predetermined periodof time elapses; and (b) after the predetermined period of time elapses,producing foam in the space using air available in the space at asuitable speed for filling the space and extinguishing the fire.
 2. Amethod as claimed in claim 1, wherein said predetermined period of timeis approximately 30 seconds.
 3. A method as claimed in claim 1, whereinthe step of producing foam comprises producing foam in such an amountthat a foam level in the space rises with a speed of at leastapproximately 1.5 meters/minute.
 4. A method for extinguishing a fire ina closed or open space using water and foam, comprising the steps of:(a)initially producing water mist using air available in the space until atemperature of combustion gases of the fire has dropped to apredetermined temperature; and (b) after the temperature in thecombustion gases has dropped to a predetermined temperature, producingfoam in the space using air available in the space at a suitable speedfor filling the space and extinguishing the fire.
 5. A method as claimedin claim 4, wherein said predetermined temperature is betweenapproximately 300° C. and approximately 400° C.
 6. A method as claimedin claim 4, wherein the step of producing foam comprises producing foamin such an amount that a foam level in the space rises with a speed ofat least approximately 1.5 meters/minute.
 7. Apparatus for extinguishingfires in open or closed spaces using water and foam, comprising:(a) atleast one fire indicator in the space to be protected; (b) at least oneunit for production of water mist and foam without air supply fromoutside; (c) a water supply pipe for supply of water to said at leastone unit; (d) a foam liquid supply pipe for supply of foam liquid tosaid water supply pipe; and (e) a control valve in said foam supply pipefor controlling the supply of foam according to a temperature ofcombustion gases produced by the fire.
 8. Apparatus for extinguishingfires in open or closed spaces using water and foam, comprising:(a) atleast one fire indicator in the space to be protected; (b) at least oneunit for production of water mist and foam without air supply fromoutside; (c) a water supply pipe for supply of water to said at leastone unit; (d) a foam liquid supply pipe for supply of foam liquid tosaid water supply pipe; and (e) a control valve in said foam supply pipefor controlling the supply of foam according to an elapsed period oftime from the start of water mist production.